The present application claims priority under 35 U.S.C. xc2xa7119 to Japanese Patent Application No. 2001-105719, filed on Apr. 4, 2001, the entire contents thereof are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an improvement in an exhaust system structure for a motorcycle.
2. Description of Background Art
Exhaust system structures for motorcycles are arranged such that exhaust gases emitted from an engine disposed between front and rear wheels are discharged through an exhaust pipe and a silencer into the atmosphere. One such exhaust system structure for motorcycles is known from Japanese utility model publication No. 2-10071 entitled xe2x80x9cMotorcycle with cowlingxe2x80x9d (hereinafter referred to as xe2x80x9cprior art 1xe2x80x9d).
As shown in FIG. 2 of the publication of the prior art 1, the prior art 1 relates to an exhaust system structure in which an exhaust pipe 32 extends rearward from an engine 23 disposed between a front wheel 11 and a rear wheel 14, and a muffler 34 is connected to the rear end of the exhaust pipe 32 (the reference numerals are those cited in the publication). Therefore, the muffler 34 is disposed laterally of an upper portion of the rear wheel 14.
With the prior art 1, since the muffler 34 which is a heavy object is disposed in an upper portion of the motorcycle body, the center of gravity of the motorcycle body tends to be elevated. Because the muffler 34 which is a heavy object is disposed in a rear portion of the motorcycle body, the weight of the motorcycle body needs to be balanced in its longitudinal direction in order to increase the maneuvering capability of the motorcycle.
To solve the above problems, an arrangement disclosed in Japanese laid-open patent publication No. 58-6912 entitled xe2x80x9cSilencer device for motorcyclexe2x80x9d (hereinafter referred to as xe2x80x9cprior art 2xe2x80x9d) may be employed.
As shown in FIG. 1 of the publication of the prior art 2, the prior art 2 relates to an exhaust system structure in which an engine 11 is disposed between a front wheel (no reference numeral) and a rear wheel 13, a muffler body 14 is disposed beneath the engine 11, an exhaust pipe 12 extends downwardly from a front portion of the engine 11, a gas inlet in the front portion of the muffler body 14 is connected to the exhaust pipe 12, and exhaust gases are discharged from a gas outlet in the rear portion of the muffler body 14.
According to the prior art 2, since the muffler body 14 which is a heavy object is disposed in a low position near the engine 11, the center of gravity of the motorcycle body is lowered. The layout is advantageous in balancing the weight of the motorcycle body in its longitudinal direction.
Motorcycles include medium and large-size motorcycles which can be driven at high speeds. For motorcycles to be able to be driven at high speeds, high-output engines may be installed thereon. For performing the capabilities of such a high-output engine, it is necessary for the exhaust pipe 12 to have at least a certain length. However, because the muffler body 14 is disposed near the engine 11 according to the prior art 2, it is difficult to increase the length of the exhaust pipe 12 simply by elongating the exhaust pipe 12.
It is therefore an object of the present invention to provide a technique for
(1) maintaining the length of an exhaust pipe in order to sufficiently perform the capabilities of an engine, and
(2) placing a silencer which is a heavy object in a position advantageous to lower the center of gravity of a motorcycle body and balance the weight of the motorcycle body in its longitudinal direction.
To achieve the above object, there is provided in accordance with claim 1 an exhaust system structure in a motorcycle having an engine disposed between front and rear wheels, an exhaust pipe extending from the engine, and a silencer connected to the exhaust pipe for discharging exhaust gases, characterized in that said silencer is of the type having a gas outlet disposed near a gas inlet, the silencer is disposed below the engine with the gas inlet facing toward the rear wheel, and the exhaust pipe extends to a position near the rear wheel and is connected to the gas inlet of said silencer.
Since the silencer whose gas inlet faces toward the rear wheel is disposed below the engine and the exhaust pipe extends to a position near the rear wheel and is connected to the gas inlet of the silencer, the exhaust pipe extending from the engine to the gas inlet is elongated. Since a long exhaust pipe is used, the engine capability is sufficiently performed even if the engine is a high-output engine.
Because the silencer which is a heavy object is disposed below the engine that is disposed between the front and rear wheels, the center of gravity of the motorcycle body is lowered to reduce the inertia of rolling. Further, this layout is advantageous in keeping the weight of the motorcycle body in balance in its longitudinal direction.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.